Joe Mauer is healthy enough to start, but will get tonight's game off.
Lefty Cliff Lee is on the hill for the Indians, so the Twins will sit Mauer and start Mike Redmond.
Source: Minneapolis Star-Tribune

From Rototimes:

Although Joe Mauer (C) Min returned from his tight groin last night, he will be given today off and be back behind the plate tomorrow, according to the Pioneer Press.